Conventionally, such engines whether they are of the reciprocating piston type or the rotary type, utilize the Otto cycle or the Diesel cycle or the Dual Combustion cycle.
All conventional engines suffer from one principal disadvantage, namely, that the expansion stroke is the same length as the compression stroke so that a considerable amount of energy is wasted and expelled as hot exhaust gases under considerable pressure.
Another disadvantage of conventional engines is that they require a separate combustion chamber for each piston.